System and method for controlling temperature and humidity of a controlled space

ABSTRACT

A system for controlling temperature and humidity of a controlled space includes a supply air path for supplying an outside air stream to the controlled space; an exhaust air path for conveying an exhaust air stream from the controlled space; a total energy recovery device in contact with the outside air stream and the exhaust air stream; a dehumidification wheel in contact with two spaced portions of the outside air stream; and a cooler in contact with the outside air stream between the two spaced portions.

BACKGROUND OF THE INVENTION

The invention relates to the field of heating, ventilation and airconditioning and, more particularly, to a system and method forcontrolling temperature and humidity of a controlled space.

Uniform standards have been set for minimum treatment of air forconditioning controlled spaces. Two of these standards are ASHRAE/ANSIStandard 90.1 and ASHRAE/ANSI Standard 62, which prescribe basic energyefficiency requirements and minimum amounts of outside air to maintainacceptable indoor air quality. Standard 90.1 requires the use of a totalenergy recovery device when more than 5000 CFM (and greater than 70%) ofoutside air is being introduced into a space. Problems arise in hot andhumid climates, where introducing large amounts of outdoor air canactually be detrimental to indoor air quality.

Attempts have been made to address this issue. U.S. Pat. No. 6,199,388is drawn to a system and method for controlling temperature and humidityin a controlled space. However, other attempts at solving this problemstill require excessive amounts of mechanical cooling.

The need remains for a system and method for controlling temperature andhumidity in a controlled space with reduced requirements for mechanicalcooling.

It is therefore the primary object of the present invention to providesuch a system and method.

Other objects and advantages of the present invention appear herein.

SUMMARY OF THE INVENTION

According to the invention, the foregoing objects and advantages havebeen attained.

In accordance with the invention, a system for controlling temperatureand humidity of a controlled space is provided, comprising a supply airpath for supplying an outside air stream to the controlled space; anexhaust air path for conveying an exhaust air stream from the controlledspace; a total energy recovery device in contact with the outside airstream and the exhaust air stream; a dehumidification wheel in contactwith two spaced portions of the outside air stream; and a cooler incontact with the outside air stream between the two spaced portions.

In further accordance with the invention, a method is provided

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of preferred embodiments of the present inventionfollows, with reference to the attached drawings, wherein:

FIG. 1 schematically illustrates an embodiment of the invention; and

DETAILED DESCRIPTION

The invention relates to the field of heating, ventilation and airconditioning (HVAC) and more particularly to a system and method forcontrolling temperature and humidity of a controlled space. The systemand method of the invention can utilize 100% outside air, and requiresless mechanical cooling than other systems.

FIG. 1 shows a system 10 which includes an outside air inlet 12, anexhaust air outlet 14, a supply air duct 16 for feeding conditioned airto the controlled space (not illustrated), and a return air duct 18 forreturn air from the controlled space. The system defines a supply airpath which conveys outside air from inlet 12 to supply air duct 16, andan exhaust air path which conveys exhaust air from return air duct 18 tooutlet 14.

As shown in FIG. 1, the exhaust air path is parallel to a portion of thesupply air path, and the paths are separated by a duct wall 19.

A total energy recovery device 20 is positioned to contact air in boththe supply air path and the exhaust air path. Device 20 is referred toas a total energy recovery device because it transfers both sensible andlatent energy from one side to the other. Thus, device 20 serves toremove sensible and latent energy from air in the supply air path, andtransfers this sensible and latent energy to air in the exhaust airpath.

Device 20 can preferably be an enthalpy wheel such as is described inU.S. Pat. No. 4,582,129 and/or 4,769,053, for example, but may be anyother device that can transfer both sensible and latent energysimultaneously. Such a wheel can be set to rotate at speeds which varydepending upon temperature and humidity adjustment desired for aspecific application, and also upon specific characteristics of thewheel. Typically, this device can be rotated at speeds of between about8 and up to in excess of 30 revolutions per minute.

After passing a portion of the exhaust air path, the supply air pathcontinues to a turn manifold 22 or other type of turn path to doubleback upon itself as shown in FIG. 1. This defines two parallel portionsof the supply air path which are spaced along the path.

A dehumidification wheel 24 can be positioned to contact air in thesupply air path at the two spaced locations, and a cooling coil 26 canbe positioned along the supply air path between the two contact pointsof wheel 24 with air in the supply air path.

Dehumidification wheel 24 can suitably be any device which removeslatent energy (moisture) from one air stream and passes it to another.This can for example be a desiccant-coated wheel as may be known to aperson skilled in the art.

The turn manifold 22 of the supply air path as discussed allows air tobe contacted with a first side of wheel 24, then with cooling coil 26,and then with the other side of wheel 24. Thus, wheel 24 in thisembodiment rotates through two spaced portions of the supply air pathand serves first to cool and humidify the supply air, and then reheatand further dehumidify the cooled air from cooling coil 26.

Also shown in FIG. 1 are typical examples of the condition of air atvarious points along the supply air and exhaust air paths. Assuming thatoutside air is obtained at 95° F. DB and 78° F. WB (117.97 grains/lb),this air can be treated at one side of device 20 to temper the outsideair and produce air at 80.9° F. DB and 66.8° F. WB (75 grains/lb). Thistempered stream of air then reaches the first side of wheel 24, and thiswheel serves to cool the tempered air to produce cooled air at 70.5° F.DB and 65.4° F. WB (85.5 grains/lb). This cooled air then flows pastcooling coil 26 and is mechanically cooled to produce sub-cooled air at50° F. DB and 49° F. WB (50 grains/lb).

Sub-cooled air from cooling coil 26 then passes the other side of wheel24 and is reheated to 60.5° F. DB and 50.8° F. WN (39.5 grains/lb). Thisreheated stream of air can then be fed to the controlled space as supplyair, and/or can be fed to a re-heat coil 28 which can be positionedalong the supply air path between the second side of wheel 24 and thesupply air outlet 16.

Air is also removed from the controlled space, and this air is referredto as return air. Return air is drawn from the controlled space throughreturn air duct 18, for example at 75° F. DB and 62.5° F. WB (64.4grains/lb). Passing the other side of device 20 increases thetemperature and humidity of exhaust air passing thereby to produceexhaust air at 89° F. DB and 74° F. WB (101.4 grains/lb).

FIG. 1 shows a fan 30 which drives air along the supply air path. Fan 30is shown in a particularly suitable location, but can alternatively bepositioned at any location which serves to keep the air flowing at adesired speed, preferably without significantly contributing to heatand/or moisture already present in the air stream.

A further air handler 32, in this illustration an exhaust fan, can alsobe positioned along the exhaust path for driving air along the exhaustpath if desired.

A system as illustrated in FIG. 1 can produce a supply air temperatureof 60.5° F. DB/50.8° F. WB at 5000 CFM with less than 20 tons ofmechanical cooling capacity. Under like circumstances, a conventionalair conditioning system could require 50 tons of mechanical coolingcapacity, and a standard dual wheel system could require 30 tons ofmechanical cooling capacity. Further, the system of the presentinvention will produce extremely low dew point supply air even underpart load conditions.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

1. A system for controlling temperature and humidity of a controlledspace, comprising: a supply air path for supplying an outside air streamto the controlled space; an exhaust air path for conveying an exhaustair stream from the controlled space; a total energy recovery device incontact with the outside air stream and the exhaust air stream; adehumidification wheel in contact with two spaced portions of theoutside air stream; and a cooler in contact with the outside air streambetween the two spaced portions, wherein the supply air pathsequentially passes the total energy recovery device, thedehumidification wheel, the cooler, and then the dehumidification wheelagain before reaching the controlled space.
 2. The system of claim 1,wherein the supply air path further comprises a turn manifold forconveying the outside air stream from one side of the dehumidificationwheel past the cooler and to the other side of the dehumidificationwheel.
 3. The system of claim 1, wherein the total energy recoverydevice comprises an enthalpy wheel positioned to rotate through theoutside air stream and the exhaust air stream.
 4. The system of claim 1,wherein the dehumidification wheel comprises a desiccantdehumidification wheel.
 5. The system of claim 1, wherein the coolercomprises a cooling coil positioned along the outside air stream.
 6. Thesystem of claim 1, further comprising a reheat coil downstream of thedehumidification wheel.
 7. The system of claim 6, wherein thedehumidification wheel rotates through the two spaced portions, andwherein the reheat coil is downstream of both spaced portions.
 8. Thesystem of claim 1, wherein the exhaust air path and a portion of thesupply air path are substantially co-linear.
 9. A method for operatingthe system of claim 1, comprising: driving the outside air stream alongthe supply air path; using the total energy recovery device to transferenergy from the outside air stream to the exhaust air stream; using thedehumidification wheel to further cool the outside air stream at a firstof said two spaced portions; further cooling the outside air stream withsaid cooler; reheating the outside air stream at the second of the saidspaced portions; and adding energy to the exhaust air stream via thetotal energy recovery device.
 10. The system of claim 1 wherein: themeans for dehumidifying comprises a wound silica gel desiccant wheel.11. The system of claim 1 wherein: the total energy recovery devicecomprises an enthalpy wheel.
 12. A system for controlling temperatureand humidity of a controlled space, comprising: a supply air path forsupplying an outside air stream to the controlled space; an exhaust airpath for conveying an exhaust air stream from the controlled space;means for recovering energy in contact with the outside air stream andexhaust air stream; means for dehumidifying in contact with two spacedportions of the outside air stream; and means for cooling in contactwith the outside air stream between the two spaced portions, wherein thesupply air path extends from an outside air inlet sequentially throughthe means for recovering, the means for dehumidifying, the means forcooling, and the means for dehumidifying again before reaching thecontrolled space.
 13. The system of claim 12 wherein the means forrecovering energy comprises an enthalpy wheel positioned to rotatethrough the outside air stream and the exhaust air stream.
 14. Thesystem of claim 13 wherein the means for dehumidifying comprises adesiccant dehumidification wheel.
 15. The system of claim 14 wherein themeans for cooling comprises a cooling coil.
 16. The system of claim 15further comprising: means for reheating downstream of the means fordehumidifying.
 17. The system of claim 12 wherein: a leg of the supplyair path through the means for dehumidifying downstream of the means forcooling is substantially co-linear with a leg of the exhaust air paththrough the means for recovering energy.
 18. The system of claim 12wherein: the means for dehumidifying comprises a wound silica geldesiccant wheel.
 19. A system for controlling temperature and humidityof a controlled space, comprising: a supply air path for supplying anoutside air stream to the controlled space; an exhaust air path forconveying an exhaust air stream from the controlled space; a totalenergy recovery device in contact with the outside air stream and theexhaust air stream; a dehumidification wheel in contact with two spacedportions of the outside air stream; a reheat coil downstream of thedehumidification wheel, wherein the dehumidification wheel rotatesthrough the two spaced portions, and wherein the reheat coil isdownstream of both spaced portions; and a cooler in contact with theoutside air stream between the two spaced portions.
 20. The system ofclaim 19 wherein the supply air path further comprises a turn manifoldfor conveying the outside air stream from one side of thedehumidification wheel past the cooler and to the other side of thedehumidification wheel.